The main indictor of kidney damage is protein in the urine, a condition known as proteinuria or albuminuria. The protein involved in diabetic nephropathy is called albumin; this is one of the primary proteins normally present in the blood.
Up to 20% of patients with type 2 diabetes and 40% of patients with type 1 diabetes have higher than normal amounts of protein in their urine. Microalbuminuria is a condition characterized by small amounts of albumin in the urine. If untreated, the amounts of albumin in the urine can increase, which is called macroalbuminuria, and eventually this results in kidney failure.
Diabetic nephropathy is more common in African-Americans, Mexican-Americans and Pima Indians. It is also more likely to occur within siblings, that is, those who have another sibling with diabetic nephropathy.
Symptoms of Diabetic Nephropathy
Typically there are no symptoms when the kidneys first begin to "spill" protein into the urine. As the severity of nephropathy progresses, the person may start to experience the effects of more advanced kidney disease, including reduced urination, unusual fatigue, confusion, and high blood potassium levels, which can lead to potentially dangerous heart rhythm problems.
Diagnosing Diabetic Nephropathy
Screening for diabetic nephropathy should start within five years of a diagnosis of type 1 diabetes, or at the onset of puberty, whichever comes first. Screening for diabetic nephropathy in people with type 2 diabetes should take place within one year of diagnosis. All people with diabetes should then be screened annually, particularly after microalbuminuria has been detected.
Diabetic nephropathy and microalbuminuria are best diagnosed with a urine sample. It is important to avoid urine testing during an ongoing urinary tract infection or another acute illness, after strenuous exercise, or with uncontrolled high blood pressure or heart failure. Any of these conditions can cause blood and albumin to show up in the urine, resulting in an inaccurate measurement.
Healthcare providers may quickly check urine using a dipstick to give a rough assessment of proteinuria or albuminuria. If a dipstick measurement is abnormal, the doctor may request a 24-hour urine collection for further assessment. On rare occasions patients with proteinuria may need a more invasive test, such as a kidney biopsy.
Other screenings to evaluate diabetic nephropathy involve cardiovascular factors, such as hypertension, heart failure and, importantly, retinopathy (eye damage). Because diabetic retinopathy and diabetic nephropathy both arise from damage to the small blood vessels, they often exist in concert.
Treatment of Diabetic Nephropathy
The first line of defense against diabetic nephropathy is a healthy lifestyle, including a low-fat diet, light-to-moderate exercise regimen, smoking cessation, and avoiding excessive alcohol consumption in an effort to keep blood sugar levels in check and reduce blood pressure.
Albuminuria can be reversed by taking certain blood pressure medications, such as angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers, which are particularly beneficial for both lowering blood pressure and protecting the kidneys in people with diabetes. A blood pressure under 130/80 mmHg should be targeted by people with diabetes. Reaching this goal often requires taking more than one blood pressure medication.
Another important factor in managing diabetic nephropathy is to keep blood sugars in check using insulin and possibly other medications as well. The target A1C level (a measure of average blood sugar levels during the last few months) for a patient with diabetic nephropathy is less than 7%.
Along with managing blood pressure and blood sugars, patients with diabetic nephropathy also benefit from lowering cholesterol and preventing obesity. There is some evidence that reducing protein in the diet will help prevent the progression of kidney disease. There is, however, some controversy regarding this theory.
Who Will Need Dialysis for Nephropathy?
Approximately 40% of patients starting dialysis (a treatment that filters and cleans the blood when the kidneys are no longer able to do so) can attribute their kidney failure to diabetic nephropathy. However, this represents a small minority of all diabetic patients. Although there is limited information reflecting current treatment principles with excellent blood pressure and blood sugar control, and the use of ACE inhibitors, a few small studies indicate that fewer than 10% of those with diabetes will ever require dialysis.
When to See a Kidney Specialist
Once it has been determined that albuminuria is present in the urine, the healthcare provider will measure the glomerular filtration rate (GFR), which indicates how well the kidneys are working. When the GFR drops to the point that indicates a significant decline in kidney function, a nephrologist (kidney specialist) should be consulted. The nephrologist will become part of the healthcare team to determine the best way to protect the kidneys from further damage, and to identify any needs for further treatment, such as dialysis.
The American Diabetes Association recommends that diabetic patients have their GFR measured annually.
LifeWire, a part of The New York Times Company, provides original and syndicated online lifestyle content. Heather M. Ross, MS, APRN, NP is an adult nurse practitioner specializing in cardiovascular care. She is a widely published author and lecturer in the fields of cardiac electrophysiology and heart failure. Ms. Ross lives in Paradise Valley, Ariz.
